edac: mpc85xx mask ecc syndrome correctly

With a 64-bit wide data bus only the lowest 8-bits of the ECC syndrome are
relevant.  With a 32-bit wide data bus only the lowest 16-bits are
relevant on most architectures.

Without this change, the ECC syndrome displayed can be mildly confusing,
eg:

  EDAC MPC85xx MC1: syndrome: 0x25252525

When in reality the ECC syndrome is 0x25.

A variety of Freescale manuals say a variety of different things about how
to decode the CAPTURE_ECC (syndrome) register.  I don't have a system with
a 32-bit bus to test on, but I believe the change is correct.  It'd be
good to get an ACK from someone at Freescale about this change though.

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
Signed-off-by: Doug Thompson <dougthompson@xmission.com>
Cc: Kumar Gala <galak@gate.crashing.org>
Cc: Dave Jiang <djiang@mvista.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 14 insertions, 1 deletions

diff --git a/drivers/edac/mpc85xx_edac.c b/drivers/edac/mpc85xx_edac.c
index ecd5928d7110..6d0114a1b77e 100644
--- a/drivers/edac/mpc85xx_edac.c
+++ b/drivers/edac/mpc85xx_edac.c
@@ -672,6 +672,7 @@ static void mpc85xx_mc_check(struct mem_ctl_info *mci)
 {
         struct mpc85xx_mc_pdata *pdata = mci->pvt_info;
         struct csrow_info *csrow;
+        u32 bus_width;
         u32 err_detect;
         u32 syndrome;
         u32 err_addr;
@@ -692,6 +693,15 @@ static void mpc85xx_mc_check(struct mem_ctl_info *mci)
         }
 
         syndrome = in_be32(pdata->mc_vbase + MPC85XX_MC_CAPTURE_ECC);
+
+        /* Mask off appropriate bits of syndrome based on bus width */
+        bus_width = (in_be32(pdata->mc_vbase + MPC85XX_MC_DDR_SDRAM_CFG) &
+                        DSC_DBW_MASK) ? 32 : 64;
+        if (bus_width == 64)
+                syndrome &= 0xff;
+        else
+                syndrome &= 0xffff;
+
         err_addr = in_be32(pdata->mc_vbase + MPC85XX_MC_CAPTURE_ADDRESS);
         pfn = err_addr >> PAGE_SHIFT;
 
@@ -707,7 +717,7 @@ static void mpc85xx_mc_check(struct mem_ctl_info *mci)
         mpc85xx_mc_printk(mci, KERN_ERR, "Capture Data Low: %#8.8x\n",
                           in_be32(pdata->mc_vbase +
                                   MPC85XX_MC_CAPTURE_DATA_LO));
-        mpc85xx_mc_printk(mci, KERN_ERR, "syndrome: %#8.8x\n", syndrome);
+        mpc85xx_mc_printk(mci, KERN_ERR, "syndrome: %#2.2x\n", syndrome);
         mpc85xx_mc_printk(mci, KERN_ERR, "err addr: %#8.8x\n", err_addr);
         mpc85xx_mc_printk(mci, KERN_ERR, "PFN: %#8.8x\n", pfn);
 
diff --git a/drivers/edac/mpc85xx_edac.h b/drivers/edac/mpc85xx_edac.h
index 52432ee7c4b9..cb24df839460 100644
--- a/drivers/edac/mpc85xx_edac.h
+++ b/drivers/edac/mpc85xx_edac.h
@@ -48,6 +48,9 @@
 #define DSC_MEM_EN      0x80000000
 #define DSC_ECC_EN      0x20000000
 #define DSC_RD_EN       0x10000000
+#define DSC_DBW_MASK    0x00180000
+#define DSC_DBW_32      0x00080000
+#define DSC_DBW_64      0x00000000
 
 #define DSC_SDTYPE_MASK         0x07000000